EPDM composition

Abstract

The EPDM composition is a rubber composition obtained by blending carbon black, a plasticizer and a cross-linking agent in an ethylene-propylene-diene ternary copolymer rubber, the plasticizer is a polyol ester, the polyol ester is a reaction product of a neopentyl polyol and a monocarboxylic acid, and the amount of the plasticizer in the composition is 5-22 wt%. The EPDM composition does not damage the mixing property and the processability, and the hardness change of the obtained cross-linked product after a thermal aging test is the same as that of the cross-linked product under the condition of matching the same parts of alpha-olefin oligomer, and is greatly improved compared with that of the cross-linked product under the condition of matching aliphatic dibasic acid ester.

Description

Technical Field

[0001] The present invention relates to an EPDM composition, and more particularly to an EPDM composition that can be used as a molding material such as an anti-vibration rubber for automobiles. Background Art

[0002] Anti-vibration rubber for automobiles is indispensable in preventing the vibration and noise generated by the engine and the vibration and noise received from the road during driving from being transmitted to the interior of the vehicle. Recently, due to the trend of high efficiency and space saving of automobile engines, the heat resistance environment near the engine room or around the exhaust pipe has become more severe than before.

[0003] When anti-vibration rubber is thermally degraded, not only will the anti-vibration and vibration damping functions be reduced due to an increase in spring constant and elastic modulus, but also durability will be deteriorated due to a decrease in strength and elongation. Therefore, in order to maintain the functions of the products to which it is applied, anti-vibration rubber is required to have high heat resistance.

[0004] On the other hand, when a car is used in an extremely low temperature environment, the spring constant or elastic modulus of the anti-vibration rubber may increase due to the rubber material being close to the glass state, and the anti-vibration function and vibration reduction function may be reduced. From this point of view, low temperature resistance has also become one of the important requirements for anti-vibration rubber for automobiles.

[0005] Here, EPDM is a well-balanced polymer that has both high heat resistance and excellent low-temperature properties. Usually, EPDM is used as a base polymer, and other fillers and plasticizers are compounded to optimize the heat resistance and low-temperature properties of anti-vibration rubber for automobiles.

[0006] As methods for improving the low temperature properties of EPDM, there are known methods of mixing α-olefin oligomers (Patent Document 1, etc.) and methods of mixing aliphatic dibasic acid esters (Patent Document 2, etc.). However, although the method of mixing aliphatic dibasic acid esters is very excellent in low temperature properties, the oxygen atom of the carbonyl group takes away the β-hydrogen atom from the alcohol, which leads to easy thermal degradation and tends to significantly impair the heat resistance of the rubber material. In addition, when mixing α-olefin oligomers, although the balance between low temperature properties and heat resistance is excellent, these two characteristics are sought to be further improved in accordance with the recent requirements of higher standards.

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: WO2005 / 057045

[0010] Patent Document 2: Japanese Patent Application Publication No. 2005-172165 Summary of the invention

[0011] Technical problem to be solved by the invention

[0012] The object of the present invention is to provide an EPDM composition which can be used to prepare a rubber having a good balance between low temperature resistance and heat resistance, such as a vibration-damping product for a crankshaft or a transmission shaft and an anti-vibration rubber for various assembly products.

[0013] Solutions to Solve Problems

[0014] The above-mentioned object of the present invention is achieved by an EPDM composition, which is a rubber composition formed by mixing carbon black, a plasticizer and a crosslinking agent into an ethylene-propylene-diene ternary copolymer rubber, wherein the plasticizer is a polyol ester, which is a reaction product of a neopentyl polyol and a monocarboxylic acid, and the amount of the plasticizer in the composition is 5% by weight to 22% by weight.

[0015] Effects of the Invention

[0016] The EPDM composition of the present invention has the following excellent effects: the kneading property and processability are not impaired, and the hardness change of the obtained cross-linked product after the heat aging test is comparable to that of the case where the same amount of α-olefin oligomer is added, and is greatly improved compared to the case where an aliphatic dibasic acid ester is added.

[0017] Furthermore, as shown in the examples and comparative examples described later, in the test of the temperature dependence of the viscoelastic modulus, the ratio of the elastic modulus E' at -30°C to the elastic modulus E' at 60°C, i.e., E' (-30°C / 60°C), is not as good as when an aliphatic dibasic acid ester is added, but it is superior in low temperature properties compared to when an α-olefin oligomer is added.

[0018] The reason for these effects is that the polyol ester, which is the reaction product of neopentyl polyol and monocarboxylic acid, is compatible with EPDM, thereby improving the molecular mobility in the rubber material and improving low temperature properties. At the same time, since the polyol ester has a structure that is not easily thermally degraded, it does not hinder the heat resistance of the material. DETAILED DESCRIPTION

[0019] As the ethylene-propylene-diene ternary copolymer rubber (EPDM), any rubber obtained by copolymerizing ethylene and propylene with a small amount of various diene components can be used. In practice, various commercially available EPDMs such as the EP series produced by JSR and the Keltan series produced by ARLANXEO can be used directly.

[0020] As carbon black, furnace black generally used as a reinforcing agent can be used, and preferably carbon black having a nitrogen adsorption specific surface area of ​​20 m 2 / g~240m 2 / g, DBP oil absorption of 40ml / 100g to 180ml / 100g of carbon black, such as HAF carbon black, FEF carbon black, etc. Carbon black is used in the EPDM composition at a ratio of about 20% to 40% by weight, preferably about 25% to 40% by weight. When carbon black is used in a ratio less than the above range, the reinforcement becomes smaller and it becomes difficult to meet the basic rubber material properties. On the other hand, when it is used in a ratio greater than the above range, the aggregation of carbon black sometimes has an adverse effect on the rubber material properties, so it is not preferred.

[0021] As a plasticizer, a polyol ester composed of a neopentyl polyol and a monocarboxylic acid (from the viewpoint of low temperature properties, preferably a polyol ester which is a reaction product of a trivalent neopentyl polyol such as trimethylolpropane and a linear monocarboxylic acid having 5 to 15 carbon atoms, more preferably 5 to 12 carbon atoms) is added to the EPDM composition at a ratio of about 5 to 22% by weight (for example, 8 to 40 parts by weight per 100 parts by weight of EPDM), preferably about 5 to 19% by weight. Since the polyol ester composed of a neopentyl polyol and a monocarboxylic acid does not have a β-hydrogen atom derived from alcohol in the molecular structure, it is not easily thermally degraded and has excellent heat resistance and low temperature properties. In practice, commercially available products such as Unister H-327R and H-334R manufactured by NOF Corporation can be used as they are.

[0022] Here, the composition used as the basis for calculating the weight ratio of the plasticizer, etc. corresponds to a composition containing an acid acceptor, a lubricant, an anti-aging agent, and a co-crosslinking agent in addition to carbon black, a plasticizer, and a crosslinking agent in an ethylene-propylene-diene ternary copolymer rubber. Even if other compounding ingredients are added, these other compounding ingredients are not included in the total weight of the composition used as the basis for calculating the weight ratio of the plasticizer, etc. When the amount of the polyol ester added to the composition is less than 5% by weight, the effect of improving the low temperature properties is small. On the other hand, when it exceeds 22% by weight, the productivity and processability of the rubber material deteriorate, and the polyol ester precipitates from the crosslinked product.

[0023] As an organic peroxide crosslinking agent, an organic peroxide commonly used for crosslinking of EPDM, such as dicumyl peroxide, 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane, and 2,5-dimethyl-2,5-bis(tert-butylperoxy)3-hexyne, is used in a ratio of about 0.5% to 2.5% by weight, preferably about 1.0% to 1.8% by weight in the EPDM composition.

[0024] It is preferred to use, together with an organic peroxide crosslinking agent, a commonly used multifunctional unsaturated compound such as triallyl isocyanurate, triallyl cyanurate, ethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, N,N'-m-phenylene maleimide, or 1,2-polybutadiene, and the like. These co-crosslinking agents are used in a ratio of about 1.0 to 5.0 parts by weight per 100 parts by weight of EPDM.

[0025] In addition, oxides or hydroxides of divalent metals, acid acceptors such as hydrotalcite, lubricants such as stearic acid, and commonly used antioxidants for EPDM are used in proportions of about 3.0 to 5.0 parts by weight, about 0.5 to 3.0 parts by weight, and about 0.5 to 3.0 parts by weight per 100 parts by weight of EPDM, respectively.

[0026] In addition, various compounding agents which have been widely used hitherto may be added arbitrarily to the EPDM composition in which the above-mentioned components are essential components within a range not impairing the object of the present invention.

[0027] The EPDM composition can be prepared by kneading using a kneader, roller, etc. The kneaded material is usually cross-linked and molded into the desired shape by press vulcanization at about 170°C to 190°C for about 2 minutes to 6 minutes, and then oven vulcanized at about 150°C to 180°C for about 1 hour to 5 hours (secondary crosslinking) as needed.

[0028] Example

[0029] Next, the present invention will be described with reference to examples.

[0030] Example 1

[0031]

[0032]

[0033] After mixing the above ingredients except the crosslinking agent with a closed mixer, the ingredients are transferred to an open roll, the crosslinking agent is added thereto, and after further mixing, pressure vulcanization is performed at 180°C for 6 minutes and oven vulcanization is performed at 150°C for 5 hours to obtain a crosslinked product. During mixing, it is confirmed whether mixing is possible and whether there is plasticizer precipitation. If mixing is not possible or plasticizer precipitation is confirmed, it is judged as ×. At the same time, the obtained crosslinked product is used to measure normal physical properties, heat aging resistance and elastic modulus temperature dependence. It should be noted that regarding heat aging resistance and elastic modulus temperature dependence, evaluations were also conducted when the plasticizer amount was 5.5% by weight and 18.7% by weight.

[0034] Normal physical properties: Based on JIS K6253 corresponding to ISO 48-4:2018,

[0035] Comply with JIS K6251 corresponding to ISO 37:2011

[0036] Heat aging resistance: The change in hardness Hs after heat aging at 120°C or 150°C for 70 hours was measured, and the judgment criteria were divided according to the plasticizer ratio (5.5 wt%, 12.6 wt%, and 18.7 wt% or more) and evaluated as follows

[0037] [120°C, 70 hours]

[0038]

[0039] [150°C, 70 hours]

[0040]

[0041] Temperature dependence of elastic modulus: In the temperature range of -30℃ to 60℃, E' was measured from -30℃ at a heating rate of 2℃ / min, and the value of E'(-30℃) / E'(60℃) was calculated. The evaluation was performed according to the plasticizer ratio as follows

[0042]

[0043] Example 2

[0044] In Example 1, the amount of the plasticizer was changed to 9.8 parts by weight (5.5% by weight).

[0045] Example 3

[0046] In Example 1, the amount of the plasticizer was changed to 39.1 parts by weight (18.7% by weight).

[0047] Comparative Example 1

[0048] In Example 1, no plasticizer was used.

[0049] Comparative Example 2

[0050] In Example 1, the amount of the plasticizer was changed to 5.2 parts by weight (3.0% by weight).

[0051] Comparative Example 3

[0052] In Example 1, the amount of the plasticizer was changed to 58.6 parts by weight (25.6% by weight).

[0053] Comparative Example 4

[0054] In Example 1, the amount of the plasticizer was changed to 87.9 parts by weight (34.1% by weight).

[0055] The results obtained in Examples 1 to 3 and Comparative Examples 1 to 4 are shown in Table 1 below.

[0056] Table 1

[0057]

[0058] Example 4

[0059] In Example 1, as a plasticizer, the same amount (25 parts by weight; 12.6% by weight) of polyol ester (UNISTER H-334R manufactured by NOF Products) was used.

[0060] Example 5

[0061] In Example 4, the amount of the plasticizer was changed to 9.8 parts by weight (5.5% by weight).

[0062] Example 6

[0063] In Example 4, the amount of the plasticizer was changed to 39.1 parts by weight (18.7% by weight).

[0064] Comparative Example 5

[0065] In Example 4, the amount of the plasticizer was changed to 58.6 parts by weight (25.6% by weight).

[0066] Comparative Example 6

[0067] In Example 4, the amount of the plasticizer was changed to 87.9 parts by weight (34.1% by weight) and used. The results obtained in Examples 4 to 6 and Comparative Examples 5 to 6 are shown in Table 2 below.

[0068] Table 2

[0069]

[0070] Comparative Example 7

[0071] In Example 1, the same amount (24.4 parts by weight; 12.6% by weight) of poly-α-olefin (product Durasyn 170 from INEOS Oligomers) was used as a plasticizer.

[0072] Comparative Example 8

[0073] In Comparative Example 7, the amount of the plasticizer was changed to 9.8 parts by weight (5.5% by weight).

[0074] Comparative Example 9

[0075] In Comparative Example 7, the amount of the plasticizer was changed to 39.1 parts by weight (18.7% by weight).

[0076] Comparative Example 10

[0077] In Example 1, the same amount (24.4 parts by weight; 12.6% by weight) of poly-α-olefin (product Durasyn 164 from INEOS Oligomers) was used as a plasticizer.

[0078] Comparative Example 11

[0079] In Example 1, as a plasticizer, the same amount (24.4 parts by weight; 12.6% by weight) of dioctyl sebacate (DOS, a product of Taoka Chemical Industry Co., Ltd.) was used.

[0080] Comparative Example 12

[0081] In Example 1, as a plasticizer, the same amount (24.4 parts by weight; 12.6% by weight) of diisodecyl adipate (DIDA, a product of Taoka Chemical Industry Co., Ltd.) was used.

[0082] Comparative Example 13

[0083] In Example 1, the same amount (24.4 parts by weight; 12.6% by weight) of paraffin-based process oil (Diana Process Oil PW-90, manufactured by Idemitsu Kosan) was used as a plasticizer.

[0084] Comparative Example 14

[0085] In Example 1, the same amount (24.4 parts by weight; 12.6% by weight) of paraffin-based process oil (Diana Process Oil PW-32, manufactured by Idemitsu Kosan) was used as a plasticizer.

[0086] The results obtained in the above Comparative Examples 7 to 14 are shown in Table 3 below.

[0087] Table 3

[0088]

[0089] Industrial Applicability

[0090] The cross-linked product of the EPDM composition of the present invention has an excellent balance between low temperature resistance and heat resistance, and can therefore be effectively used as a molding material for anti-vibration rubber for automobiles used in severe thermal environments and cold regions, such as vibration-damping products for crankshafts and drive shafts, and various assembly products.

Claims

1. An EPDM composition, characterized in that: The EPDM composition is a rubber composition in which carbon black, a plasticizer and a crosslinking agent are blended into an ethylene-propylene-diene ternary copolymer rubber, the plasticizer is a polyol ester, and the polyol ester is a reaction product of a neopentyl polyol and a monocarboxylic acid, and the amount of the plasticizer in the composition is 5% to 22% by weight.

2. The EPDM composition according to claim 1, wherein Polyol esters are reaction products of trivalent neopentyl-type polyols and straight-chain carboxylic acids having 5 to 15 carbon atoms.

3. The EPDM composition according to claim 2, wherein: The trivalent neopentyl-type polyol is trimethylolpropane. A cross-linked molded product, which is a cross-linked molded product of the EPDM composition according to claim 1.

5. A vibration-proof rubber, comprising the cross-linked molded product according to claim 4.

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